For security reasons, legal communication intercepting techniques are necessary. In the general communication systems, mobile stations connect to backend network directly, and have to exchange data (voice data, text data etc.) with each other via the backend network. In other words, the data exchanged between the mobile stations must be processed by the backend work. Therefore, when an inception is authorized by the court, an authorized user needs to ask the operator of the backend network for obtaining the data which is exchanged between the mobile stations and stored in the backend network.
However, in the developing 3GPP direct mode communication network, although mobile stations still connect to backend network, they exchange data with each other directly. In other words, in 3GPP direct mode communication network, the data exchange between the mobile stations will not be processed by the backend network. Accordingly, an authorized user cannot obtain the data exchanged between the mobile stations from the backend network since the data may not be stored in the backend network.
Accordingly, in order to implement lawful interception for 3GPP direct mode communication network, corresponding protocols and hardware devices differed from the general communication system are needed.